Ammonia reactions with the stored oxygen in a commercial lean NOx trap catalyst
- Research Centre Rez, Rez (Czech Republic); Institute of Chemical Technology, Prague (Czech Republic)
- Institute of Chemical Technology, Prague (Czech Republic)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Ammonia is an important intermediate of the NOx reduction in a NOx storage and reduction catalyst (aka lean NOx trap). NH3 formed under rich conditions in the reduced front part of the catalyst is transported by convection downstream to the unregenerated (still oxidized) zone of the catalyst, where it further reacts with the stored oxygen and NOx. In this paper, the kinetics and selectivity of NH3 reactions with the stored oxygen are studied in detail with a commercial Ba-based NOx storage catalyst containing platinum group metals (PGM), Ba and Ce oxides. Furthermore, steady-state NH3 decomposition, NH3 oxidation by O2 and NO, and N2O decomposition are examined in light-off experiments. Periodic lean/rich cycling is measured first with O2 and NH3, and then with NOx + O2 and NH3 to discriminate between the NH3 reactions with the stored oxygen and the stored NOx. The reaction of NH3 with the stored O2 is highly selective towards N2, however a certain amount of NOx and N2O is also formed. The formed NOx by-product is efficiently adsorbed on the NOx storage sites such that the NOx is not detected at the reactor outlet except at high temperatures. The stored NOx reacts with NH3 feed in the next rich phase, contributing to the N2O formation. Water inhibits the reactions of NH3 with the stored oxygen. On the contrary, the presence of CO2 increases the NH3 consumption. Furthermore, CO2 is able to provide additional oxygen for NH3 oxidation, forming –CO in analogy to the reverse water gas shift reaction.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Fuels, Engines and Emissions Research Center (FEERC); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). National Transportation Research Center (NTRC)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1187909
- Alternate ID(s):
- OSTI ID: 1337526
- Journal Information:
- Chemical Engineering Journal, Vol. 278; ISSN 1385-8947
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Similar Records
New operation strategy for driving the selectivity of NOx reduction to N2, NH3 or N2O during lean/rich cycling of a lean NOx trap catalyst
Effects of including a NO storage component on a TWC when using a lean spark ignition gasoline engine combined with a passive SCR system✰